In the steelmaking art it is well known to utilize conventional blast furnaces to produce molten iron for ultimate conversion to steel. It is also well known to make steel directly from iron ore and other process ingredients in a blast furnace from my prior U.S. Pat. Nos. 4,670,049 and 3,460,934.
The operation of the conventional blast furnace in making iron is well known. The furnace is charged from the top to form therein a column of iron ore, limestone and structural coke of sufficient strength to support the furnace charge to a depth of 90 to 100 feet. A hot air blast is forced through tuyeres at the bottom of the packed furnace to furnish heat and oxygen for the combustion of the coke in the furnace charge. The resulting gas passes up through the furnace shaft and reduce the ore, coke and flux to molten metal and slag, and then issues from the top of the furnace as dust-laden lean combustible gas. The column of process materials descends in the furnace shaft at a rate of about ten feet per hour as the structural coke is consumed, and molten iron and slag form a pool and separate in the bottom of the furnace. The pool is intermittently tapped to draw off the iron and slag separately.
It is also known in the prior art to utilize a furnace apparatus which directs the process ingredients through a tortuous path of travel. For example, my above mentioned U.S. Pat. No. 4,670,049 discloses a blast furnace for direct steelmaking in which process materials cascade as a continuous, free falling flow through a flow path that includes cascade step structures in the furnace shaft.
Additionally, U.S. Pat. No. 1,799,643 discloses a smelting furnace tower in which a radially inwardly open spiral flow channel is formed in the side walls of the tower and burner nozzles are arranged tangently to the spiral channel to direct gas and flame in a downward spiraling direction. The process ingredients are caught up by the swirling blast of flame and gases and therefore follow the downwardly spiraling channel.
U.S. Pat. No. 748,561 discloses a smelting furnace which incorporates an elongated declining smelting path with straight sections joined by sharp turns, and into which flame and gases are injected. U.S. Pat. No. 748,561 additionally discloses a furnace shaft with a varying cross section which tapers from a larger cross section adjacent the furnace entrance to a smaller cross section downstream therefrom, and breaker elements obstructing a portion of the process material flow path within the furnace chamber to retard movement of process ingredients toward the furnace outlet.